(a) Field of the Invention
The present invention relates to a folding structure of a handle for a foldable bicycle, and more particularly to one that provides a structure of bendable junction that connects the head tube below the handle and the tube pivoting to the head tube can be pulled out for the front wheel to turn in any direction relatively to the fork and the front wheel as desired, so that once the handle is turned and folded without causing the front wheel to be restricted to a fixed direction while allowing the front wheel to turn in any direction, thus to minimize the volume of the bicycle when folded.
(b) Description of the Prior Art
For bulk products, they are usually made foldable and/or retractable to minimize the space for storage, as commonly observed with a foldable bicycle, a scooter with handle, or a tricycle for children. Basically, such vehicle operated by manual is engineered with externally and internally retractable structures adapted to a longer and higher frame so to reduce the size when stored. In addition, to achieve fast and simple operation, the use of fastening parts of a quick-release wrench is widely used for the design to fix the retractable structure. Generally, a pipe strap provided with a quick-release wrench fastening the end of the external tube is designed for the retractable tube, so to fasten the end with C-shaped section of the external tube, thus to further fasten the inner tube that inserted into the external tube. A positioning means may be also provided to the pipe strap or the external tube so that the inner tube may longitudinally slide and retract in relation to the external tube without turning. Furthermore, once the retracted length still fails to reduce the size, a foldable structure is provided. In the prior art of a foldable bicycle, or a scooter with handle, a pivoting joint is connected to where between the lower end of the stem connected to the handle and the upper end of the fork pivoted through the head tube of the frame. Accordingly, the handle and the head tube connected to the pivoting joint are folded at a certain inclination to rest on either side or directly folded backward to rest over the frame. Furthermore, a great deal of RandD efforts has been also inputted into improvement of foldable bicycles (and scooter with handle). Within one of those improvements, a special insertion type of pivoting joint incorporated with a clamp of quick-release wrench is provided to the head frame as illustrated in FIG. 10. A clamp (A) composed of the quick-release wrench (A1), a pin shaft (A2), a nut (A3) and a fixation bolt (A4) incorporated with a positioning bit (B) is mounted to a structure connecting the head tube of the frame to the fork. Wherein, the positioning bit (B) has a hole (B1) bored at the center of a single flat sheet member and a small section of conic stop (B2) is formed beneath the sheet member. The combination of the positioning bit (B) and the clamp (A) is done by having placed the positioning bit (B) into an open end of the ring where the clamp (A) penetrates the ring of the quick-release wrench (A1) with the conic stop (B2) of the positioning bit (B) facing the interior of the ring of the clamp (A); the pin shaft (A2) to penetrate the open end of the ring of the clamp (A) and the hole (B1) in the positioning bit (B); and the nut (A3) to be locked to the other end of the shaft pin (A2) for both of the clamp (A) and the positioning bit (B) to connect to each other. In the structure to connect the head tube to the fork, a groove (C1) is axially provided to the upper end of the pivoting tube, a fixation hole (C2) is bored through the end of the pivoting tube, and a joint (E) is provided in relation to where the head tube (D) is inserted into the fork pivoting tube (C). The joint (E) is composed of an upper section (E1) pivoted to a lower section (E2). Both of the upper section (E1) and the lower section (E2) are each respectively inserted into a pivot (E21) and then pivoted with a rivet (E3). Two V-shaped, longitudinal chutes (E12, E22) are punched respectively on one side of the upper section (E1) and the lower section (E2) in the direction relatively to the groove (C1) of the fork pivoting tube (C). A circular chamber (E23) containing a tenon (E4) is provided inside the upper section (E1) or the lower section (E2) of the joint (E) (the lower section (E2) as illustrated). As illustrated in FIG. 11, the tenon (E4) is contained in a case (E43) having a coil (E41) to hold against a steel ball (E42). A channel (E13) is provided on a tongue (E11) protruding from the upper section (E1) in relation to the steel ball (E42) of the tenon (E4). When assembled as illustrated in FIG. 11, the clamp (A) is inserted to the upper end of the fork pivoting tube (C) and the fixation bolt (A4) is secured in the fixation hole (C2) at the end of the fork pivoting tube (C). The conic stop (B2) to the lower part of the positioning bit (B) connecting through the pin shaft (A2) pivoted to the quick-release wrench (A1) extends into the groove (C1) and held in position in the fork pivoting tube (C). Wherein, the conic stop (B2) extends to hold against the chutes (E12, E22) respectively of the upper and lower sections (E1, E2) of the joint (E) connected to the head tube (D) inside the fork pivoting tube (C) so to prevent the fork pivoting tube (C) from turning and to execute only vertical retraction. Furthermore, when both of the upper and the lower sections (E1, E2) are erected to be held in position in the channel (E13) by means of the steel ball (E42) of the tenon (E4), and the portion for insertion provided with the joint (E) below the head tube (D) is inserted into and held position in the fork pivoting tube (C), both of the upper and lower sections (E1, E2) of the joint (E) are pushed into relatively to the fork pivoting tube (C) until the upper edge of the conic stop (B2) to the lower part of the positioning bit (B) holds against and is secured in position by the upper end of the chute (E12) on the upper section (E1) of the joint (E). Then the quick-release wrench (A1) is pressed for the clamp (A) to press against the fork pivoting tube (C) and tightly fastened in relation to the integral circular portion above the chute (E12) on the upper section (E1) of the joint (E).
To fold up the handle at the head of the frame by means of the lower part of the head tube (D) for storage, the quick-release wrench (A1) is released to free the clamp (A) from fastening the fork pivoting tube (C), thus to release the upper section (E1) of the joint (E) from the head tube (D). As illustrated in FIG. 12, the head tube (D) is pulled up to ascend the joint (E) from the lower end of the head tube (D) for the upper section (E) to expose out of the upper end of the fork pivoting tube (C). Once the joint (E) is pulled up to its extreme, the positioning bit (B) incorporated to the clamp (A) restricts the joint (E) without being disengaged with its conic stop (B2) to hold against the end of the chute (E22) on the lower section (E2) of the joint (E). As illustrated in FIG. 13, a front wheel must be rotated facing either side for a proper angle jointly by the handle and the head tube (D) through the connection of the joint (E) and the fork pivoting tube (C) to change the folding direction. Accordingly, the laterally extended T-shaped handle is turned for approximately 90 degrees. Finally, the substantial part of the frame including the head tube (D), the handle is pivoted and folded downward by the upper section (E1) of the joint (E) in relation to the lower section (E2) of the joint (E) for the handle to rest on one side in front of the frame.
While being folded for storage as described above, the handle must be turned towards the front wheel is mainly due to the rotation direction of the joint (E) provided at the lower end of the head tube (D) is subject to the positioning bit (B) incorporated to the clamp (A) provided on the upper part of the fork pivoting tube (C) so to facilitate restoring to face direct front when stretched up for use of the bicycle without further adjustment required. Said design is provided with a certain convenience. However, the T-shaped handle must be turned for approximately 90 degrees to reduce the size defined by the width of the handle. Therefore, it is no way to avoid turning the front wheel. Said folding structure of course is an ideal folding structure should we neglect the space increase resulted from the front wheel turning sideways. Nonetheless, when the essence of the improvement is to minimize the storage space, the con figuration of having the head tube (D) with its joint (E), the fork pivoting tube (C) and the front wheel altogether to protrude sideways deserves a further improvement. The portable bicycle ideal for shorter-range transportation means so popular among the 9-to-5 in Japan relates to a foldable bicycle that absolutely demands the minimized size up to micrometers. The foldable bicycle requires the smaller size and the least space for storage certainly gives more market potential.
The primary purpose of the present invention is to provide a folding structure for a handle of a foldable bicycle to minimize the volume of the bicycle when folded up for storage. To achieve the purpose, a folding structure at where the lower part of the head tube under the handle connects to the fork pivoting tube can be pulled out for turning to any direction for the handle to freely rotate in relation to the fork and the front wheel, and the turning of the handle for storage will not be linked to the front wheel while the front wheel is free to turn in any direction characterized by that:
A joint is connected to the lower end of the head tube of the lower section of the handle and a clamp is inserted to the upper part of the fork pivoting tube that is pivoted through the head tube. A positioning bit is provided with a conic stop inside the positioning bit to extend into the fork pivoting tube. Said joint having its upper section pivoted to its lower section penetrates into the fork pivoting tube. A longitudinal chute is each provided respectively on the side of the upper and the lower section of the joint to receive the conic stop penetrating into the fork pivoting tube from the positioning bit. In relation to the longitudinal chute at the lower section of the joint, a circumferential groove having the same depth of the chute is formed below the chute. Using the circumferential groove, the head tube is pulled out to its extreme in relation to the fork pivoting tube for the conic stop from the positioning bit to hold against the longitudinal chute of the lower section of the joint to reach down the terminal.
Consequently, the joint is free to rotate by having the circumferential groove at the terminal of the chute on the lower section of the joint to correspond to the conic stop of the positioning bit.